Alexa Topsites: Fastest and Slowest

September 19, 2017

At Latency.at we provide performance and availability
metrics of your sites and services from multiple global locations and provides
the results as Prometheus metrics. While our users can aggregated, filtered and
graph the metrics as they wish, we deployed a Grafana + Prometheus based demo at
https://demo.latency.at. That Prometheus servers
monitors the following sites from the Alexa Topsites
List:

Unsurprisingly, the best sites are global players like Google/YouTube and Facebook.
But also small sites like my blog perform similarly with off-the-shelf CDN
configuration. For static content, low latency isn’t hard to achive after all.

Highest Latency

Now what are the worst performing sites?
topk(5, avg by (instance) (avg_over_time(probe_duration_seconds[1h])))

The globally worst performing sites target chinese customers, so global
performance isn’t a priority there. We also don’t have any probes in China yet
which would compensate that somewhat.

More surprising though, the next worst site is https://mail.live.com. That’s the
Microsoft Mail login, a service targeting a global audience. Yet, it isn’t doing
very well latency wise.

Even in the US the latency is quite bad. The origin is probably somewhere on the
east cost given the similar latency of San Francisco and Frankfurt.
If we look at the request phases we see that the request is slow across the
board.

In the typical modern web stack, handling a request touches many quite different
services. First you depend on DNS performance, then the public internet between
a client and the system that terminates the traffic, usually a reverse proxy.
The TLS handshake happens here and depends on the systems CPU mainly. After
that, the actual backend processes the request.

If we divide mail.live.com’s latency by the average latency of all sites, maybe
we can figure out which is particular slow compared to other sites:

processing and transfer times are pretty average, even a bit faster.
Everything else though is way slower than the average, with DNS resolution
taking almost an order of magnitude more time than for the average site.

If Microsoft wants to improve performance here, DNS is the place to look.